Iowa reports first case of West Nile virus this year

The Iowa Department of Health and Human Services has reported the first positive case of West Nile virus of the year in an adult in northern Iowa.

The state agency, in announcing the case Thursday, said mosquitoes across the state have tested positive for the virus, signaling a risk to Iowans.

One of those positive mosquito detections was in Johnson County. The county’s public health department announced a positive detection on Thursday.

Johnson County’s Mosquito Surveillance program, operated as a partnership between public health and Iowa State University Extension and Outreach, received the positive sample from the testing week of July 27-Aug. 2.

Rob Thul, environmental health manager for Johnson County Public Health, said the county monitors mosquitoes so it can “detect and mitigate disease risk” for residents.

“We have not seen a surveillance test come back positive since 2023, so this is nothing to worry about, but review the ways to protect ourselves,” Thul said in a statement from the county Thursday.

Last week, West Nile virus was detected in mosquitoes in Black Hawk County.

Increased levels of the virus are common at this time of year and more positive tests are likely, according to Black Hawk County Public Health.

“With the rising levels of the virus, the risk of human cases also increases,” Black Hawk County’s stated in a news release. “Therefore, residents are advised to take precautions to avoid mosquito bites.”

The Johnson County surveillance program places mosquito traps throughout the county. They are checked multiple times each week, May through September, by the county’s environmental health specialists.

Mosquitoes are collected and sent to Iowa State University for species identification. They also are tested for both West Nile virus and Zika virus.

In 2024, Iowa HHS reported 21 Iowans had been diagnosed with West Nile virus. One person died.

Human cases of the virus have been detected in Iowa every year since 2002, after the virus was found in a dead crow in Eastern Iowa in September 2001.

About West Nile virus

According to the CDC, West Nile virus is most commonly spread through the bite of an infected mosquito.

Symptoms of the virus in humans can include fever, headache, body aches, vomiting, diarrhea or rash, however only 1 in 5 people who are infected with the virus develop symptoms.

There are currently no vaccines to prevent West Nile virus in humans.

To protect against mosquito bites, Johnson County Public Health advises Iowans to wear insect repellents that are registered with the Environmental Protection Agency. The county said repellents with active ingredients like DEET, Picaridin and IR3535 are encouraged. Lemon eucalyptus oil also can help prevent bites.

In addition, it said wearing light-colored clothing and long-sleeved shirts and pants can help shield your skin as well.

“Prevention of mosquitoes spreading at home is simple, use screens on windows and doors and stop mosquitoes from laying eggs in or near water,” the county stated in a news release. “Empty anything that holds water weekly, like buckets, planters, toys, kiddie pools, birdbaths, as well as any trash containers, tires, etc. These containers should be scrubbed clean or turned over.”

Experts also say mosquito bites can be prevented by not standing in water where mosquitoes could breed, like ponds, marshes, bogs and even standing near smaller wet areas like puddles, bird baths and clogged gutters.

“Repair clogged rain gutters and turn over toys, buckets, bins and other items that catch water,” ISU’s mosquito control report stated. “Drain, fill or ditch low-lying areas that hold water for several days following a rain.”

Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues. She is also a contributing writer for the Ag and Water Desk, an independent journalism collaborative focusing on the Mississippi River Basin.

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Comments: olivia.cohen@thegazette.com